Two experiments are proposed to examine the effect of suggestion and stress on the airways, and a general model for psychosomatic asthma. The model predicts that psychological factors will affect bronchial function only among those with asthmatic obstruction primarily in mostly vagally-mediated upper airways, and that these individuals also will show greater vagal reactivity to stress. It also predicts that anxiety, repressive coping, and suggestibility/hypnotizability will predict bronchial changes resulting from psychological interventions in individuals with primarily upper-airway asthma. Site of airway obstruction in asthma will be measured by heliox lung mechanics and asthma presence/severity by the methacholine challenge test. In one experiment, subjects will be given false suggestions that they are inhaling a potent bronchoconstrictor. Effects on pulmonary function will be assessed. In another experiment, subjects will be exposed to laboratory stressors, while pulmonary and other measures of sympathetic and parasympathetic activity are taken, including respiratory sinus arrhythmia as a measure of vagal tone and urine catecholamine levels. This study will attempt to determine the relative roles of sympathetic and parasympathetic activity in the contribution to psychosomatic asthma. Subjects' perceptions of bronchoconstriction will be assessed by psychophysical scaling. Other studies will evaluate the validity of respiratory sinus arrhythmia as a measure of vagal tone among asthmatics, and the effects of theophylline medication on the dependent measures taken in the second experiment.